1. Field of the Invention
The present invention pertains to a radiation detector, a radiographic image capturing system, a radiation detection method, a radiation detection program storage medium, and a controller and particularly relates to a radiation detector, a radiographic image capturing system, a radiation detection method, a radiation detection program storage medium, and a controller that capture a radiographic image without having to synchronize with a radiation application action of a radiation applicator.
2. Description of the Related Art
Conventionally, radiographic image capturing systems that perform radiographic imaging for the purpose of medical diagnoses have been known. As one such radiographic image capturing system, there is a radiographic image capturing system that is equipped with a radiation applicator that applies radiation, a radiation detector—such as what is known as a cassette—that detects the radiation that has passed through a subject to capture a radiographic image, and a controller that controls the radiation applicator and the radiation detector.
In recent years, there have been radiation detectors using a flat panel detector (FPD) that is capable of converting the detected radiation into electrical signals. Because dark current, which contributes to noise, exists in a two-dimensional solid-state imaging device such as an FPD, the imaging time of the solid-state imaging device cannot be lengthened unreasonably. For this reason, synchronization of the application action, in which the radiation detector transmits signals to and receives signals from the radiation applicator and in which the radiation applicator applies the radiation, and the imaging action, in which the FPD performs imaging (performs detection of the radiation), is performed.
Specifically, with respect to an imaging request signal from the radiation applicator, the FPD performs initialization of the solid-state imaging device and, after the initialization has been completed, transmits an imaging preparation completion signal to the radiation applicator. After the radiation applicator receives the imaging preparation completion signal, the radiation applicator starts the application of the radiation, ends the application of the radiation after a preset application time has elapsed, and transmits an application end signal to the FPD. When the FPD receives the application end signal, the FPD ends a charge storage action by the solid-state imaging device and transitions to an output action in which the FPD outputs image data of the detected radiographic image to the controller.
In such cases as this, since the radiation applicator is hand-operated in order to control the FPD, the interface for an operator becomes complex and it is necessary to configure the radiation applicator and the FPD as a single integrated system. This leads to an increase in the size and an increase in the complexity of the device.
As a radiation detector that addresses such problems, there is a radiation detector in which the radiographic image is detected by the radiation detector without having to connect to the radiation applicator and without having to transmit signals to and receive signals from the radiation applicator (without having to synchronize with the radiation applicator). For example, Japanese Patent Application Laid-Open (JP-A) Nos. 2005-13272 and 2003-307569 disclose technologies in which the timing of the application of the radiation is determined by the FPD.
A radiation detector has been proposed that determines an application timing, which is the timing of the application of the radiation that is applied from the radiation applicator in order to capture a radiographic image of a subject, when charge information (electrical signals) that has been read out from the solid-state imaging device has reached a predetermined threshold value or greater.
In this radiation detector, there are cases in which the radiation detector may capture a radiographic image (detect image data) at a wrong timing that is originally not a correct (intended) timing when the radiation detector is to capture a radiographic image of the subject.
It is known that there are cases in which, for example, as a result of the radiation detector being dropped or the like and given an impact, electrical signals are generated just as if radiation had been applied. If the electric signals are equal to or greater than the predetermined threshold value, a radiographic image is captured even though it is not a correct timing when the radiation detector is to capture a radiographic image. The radiographic image that has been captured at an unintended timing in this way is an unintended radiographic image that is not a correct (intended) radiographic image. However, because it cannot be judged whether the radiographic image has been captured at an intended timing or has been captured at an unintended timing, the user can misunderstand that the imaging has ended by obtaining the unintended radiographic image. In cases such as this, the user may need to register the imaging menu (imaging conditions for capturing the subject, etc.) again for a retake.
The present invention provides a radiation detector, a radiographic image capturing system, a radiation detection method, a radiation detection program storage medium, and a controller that can determine whether or not a radiographic image is an image that has been detected at a correct (intended) timing.